A PLACE, as its name imports, destined for observing thc heavenly bodies; or, a building, usually erected on an eminence, for the purpose of making astronomical observations.
Almost all nations, in every age, have had their ob servatories, either public or private, in various degrees of perfection. The determination of the length of the year, and of the return of the seasons for the purposes of husbandry, and other objects, both civil and religious, were absolutely necessary in every well regulated so ciety. These, therefore, would be among the first re sults deduced from astronomical observations.
When the early navigators were prompted by their spirit for enterplise to visit distant countiies, or were driven hy storms out of sight of land, the only resource which they then possessed for ascertaining their situa tion, was a knowledge of thc places of the heavenly bodies. But the places of the sun, planets, and fixed stars, for any future period, can only be computed froni a series of observations previously made with that view; and it is by astronomy that they are deduced from ob servation and calculation, and arranged in tables, which are absolutely necessary for reducing observations taken at sea, in order to ascertain the latitude and longitude of the ship, and the variation of the compass.
As navigation, therefore, essentially depends on the determinations made in regular observatories, establish ments of this kind have been considered of great na tional importance, more especially in maritime states, and have therefore been liberally endowed by their dif ferent governments. Even private observatories have, in many places, been erected at considerable expense. 'file number of these has of late years greatly increas ed; a circumstance which, while it marks the progress of science, does honour to the enterprising character of the age.
Regular observatories are those where instruments are fixed in the meridian, by which, with the assistance of astronomical clocks, the right ascensions ancl declina tions of the heavenly bodies are determined ; and thus motion, time, and space, are made to measure each other. Such buildings and apparatus only aie called regular observatories, though very useful operations are sometimes performed, and important discoveries made, in situations where no instruments can be fixed in the meridian.
Though the information which can be drawn from an ient history is often imperfect ; yet we find that all nations, among whom astronomy has been cultivated; have had their observatories at a very early period. It cannot indeed be supposed, until considerable progress had been made both in astronomy and mechanics, that their attempts, either in constructing instruments, or erecting edifices for astronomical purposes, would be very successful. The instruments of ancient astrono mers were in general large, and of the rudest construc tion, and were formed mostly of wood, and sometimes of stone. They consisted chiefly of gnomons, dials, astro labes, and long tubes like telescopes to assist the sight. For the same purpose also deep wells were sunk in high and dry places, from the bottom of which the stars might be seen in the day time. Most of the buildings for astronomical purposes were of great height, and erected chiefly in very high situations.
We arc informed by the ancient historians, that, in Chaldea, a country highly celebrated in the early annals of astronomy, the lofty temple of Bclus was used as an observatory. In Egypt, too, the famous tomb of Osy mandias was applied to the same purpose. This build ing is said to have contained a golden circle, adapted to celestial observations, which was 365 cubits in circum ference, and one cubit in thickness. It has also been said, that the pyramids of Egypt were employed for astrono mical purposes, though this, we think, appears doubtful. In support of this opinion, it is affirmed, that they were built to face the four cardinal points. The great height of these pyramids, no doubt, is favourable for making astronomical observations, whether they be used as gnomons, or for the purpose of ascertaining accurately the times of the rising and setting of the stars. How ever this may be, it is certain that astronomy was much cultivated in Egypt, particularly in the famous school of Alexandria, where an observatory was built 300 years be fore the Christian era, and continued to flourish for more than five centuries, under a succession of celebrated names, such as, Hipparchus, Ptolemy, &c.